AQUEOUS POLYTETRAFLUOROETHYLENE EMULSION, POLYTETRAFLUOROETHYLENE FINE POWDER AND POROUS MATERIAL OBTAINED THEREFROM

• US 20080200571A1
• Filed: 04/17/2008
• Published: 08/21/2008
• Est. Priority Date: 10/17/2005
• Status: Active Grant

• Current Assignee: AGC, Inc.
• Original Assignee: Asahi Glass Company, Limited (AGC, Inc.)
• Inventors: HIGUCHI, Shinya, Hoshikawa, Jun, Kamiya, Hiroki, Matsuoka, Yasuhiko
• Granted Patent: US 7,851,573 B2
• Time in Patent Office: Days
• US Class Current: 521/65
• CPC Class Codes: C08F 14/26 Tetrafluoroethene
• CPC Class Codes: C08F 2/22 Emulsion polymerisation
• CPC Class Codes: C08F 2/26 anionic
• CPC Class Codes: Y10T 428/1376 Foam or porous material containing
• CPC Class Codes: Y10T 428/249962 Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]

Abstract

To provide an aqueous polytetrafluoroethylene (PTFE) emulsion which does not substantially contain ammonium perfluorooctanoate, and which is obtained by emulsion polymerization. Further, to provide a PTFE fine powder which is obtained from the aqueous PTFE emulsion and is excellent in a paste extrusion processability, and a porous material.

An aqueous polytetrafluoroethylene emulsion obtained by carrying out emulsion polymerization of tetrafluoroethylene alone or together with another copolymerizable monomer in an aqueous medium, wherein a fluorinated emulsifier of the formula (1):

XCF₂CF₂(O)_mCF₂CF₂OCF₂COOA

wherein X is a hydrogen atom or a fluorine atom, A is a hydrogen atom, an alkali metal or NH₄, and m is an integer of 0 or 1, is used in an amount of from 1,500 to 20,000 ppm, based on the final yield of polytetrafluoroethylene.

Claims

1. An aqueous polytetrafluoroethylene emulsion obtained by carrying out emulsion polymerization of tetrafluoroethylene alone or together with another copolymerizable monomer in an aqueous medium, wherein a fluorinated emulsifier of the formula (I):

XCF₂CF₂(O)_mCF₂CF₂OCF₂COOA

wherein X is a hydrogen atom or a fluorine atom, A is a hydrogen atom, an alkali metal or NH₄, and m is an integer of 0 or 1, is used in an amount of from 1,500 to 20,000 ppm, based on the final yield of polytetrafluoroethylene.

2. The aqueous polytetrafluoroethylene emulsion according to claim 1, wherein the average primary particle size of polytetrafluoroethylene in the aqueous polytetrafluoroethylene emulsion is from 0.18 to 0.50 μ

m.

3. The aqueous polytetrafluoroethylene emulsion according to claim 1, wherein the amount of the fluorinated emulsifier of the formula (I) is from 2,000 to 20,000 ppm, based on the final yield of polytetrafluoroethylene.

4. The aqueous polytetrafluoroethylene emulsion according to claim 1, wherein the fluorinated emulsifier of the formula (I) is CF₃CF₂OCF₂CF₂OCF₂COONH₄.

5. A polytetrafluoroethylene fine powder obtained by coagulating the aqueous polytetrafluoroethylene emulsion as defined in claim 1.

6. The polytetrafluoroethylene fine powder according to claim 5, which has a standard specific gravity of from 2.14 to 2.20.

7. A porous material of polytetrafluoroethylene obtained by paste extrusion of the polytetrafluoroethylene fine powder as defined in claim 5, followed by stretching.